This invention relates, in general, to an apparatus for raising the temperature of a gas stream; and, in particular, this invention relates to burners of the type characterized as wall mounted burners.
One particular application for the present invention is found in that portion of a combined cycle power plant referred to as a heat recovery steam generator (HRSG). A HRSG is a generally vertical free standing duct which envelops a boiler tube bundle whereby gas turbine exhaust gases are channeled through the duct in a heat exchange relationship with fluid in the tube bundle in order to raise the temperature of the tube bundle fluid to generate steam for driving a steam turbine. It is sometimes desirable to raise the temperature of the exhaust gas flow upstream from the tube bundle by using burners in which case the HRSG is referred to as being "fired". One example of a fired HRSG is given in U.S. Pat. No. 3,830,620 to Frederick J. Martin issued Aug. 20, 1974. The Martin patent shows a grid burner system which includes a network of fuel supplied burner pipes which are disposed within and across the cross-section area of the HRSG duct. Each pipe includes a plurality of fuel outlet ports on the downstream (with respect to the exhaust gas flow) surfaces of the pipes. Fuel is delivered to the outlet ports through the grid pipes and ignited by pilot burners mounted transversely to the grid pipes and downstream therefrom.
One inherent limitation in grid burner systems is the type of fuels which can be burned in order to avoid pipe clogging. Grid burner systems, in general, require natural gas or distillate fuels for operation. Grid burner systems are expensive to manufacture and install. Moreover, grid burner systems are also difficult to maintain.
A contributing factor to the aforementioned grid burner disadvantages is that the grid system is disposed within the HRSG where the hot flowing gases may cause decomposition of liquid fuels. An alternative solution to the grid burner system is a wall mounted burner which is located outside the exhaust gas duct. A wall burner shoots its flame into the duct through a port formed in one of the duct walls. Hence, the wall burner is not subject to clogging and is available for easy maintenance. One example of a prior art wall burner is given in U.S. Pat. No. 3,367,384 to Voorheis issued Feb. 6, 1968. The Voorheis burner is a liquid fuel burner wherein the totality of the fuel is supplied from a liquid fuel nozzle located upstream from a pre-main combustion chamber.